The plan: Some A-List actresses are reportedly digging into jars of baby food at mealtimes to shed pounds.

The pros and cons: As long as there's no added starch, it's just pureed vegetables, fruit, or meat—and because of the baby-size portions, not much of it. However, "it's needlessly draconian," says New York City diet expert Stephen Gullo—and don't expect to be a very popular dinner-party guest if you insist on popping your own little jars.

The bottom line: The only reasons people would lose weight eating baby food are that the portions are small and choices are limited. If you need that kind of structure, Gullo says, you'd be better off eating the same foods for lunch (try soup and a high-fiber cracker with low-fat cheese) and dinner (go with fish and salad or green vegetables) every single day. "This serves the same purpose by taking away day-to-day decisions, but it tastes better and provides you with food you're less likely to tire of," says Gullo.

The plan: Eat four to seven special protein-packed diet cookies a day (500 to 600 calories total) and one meal consisting of lean protein and vegetables (another 300 calories). (The original cookie diet was introduced in the 1970s by Sanford Siegal, but since then several similar plans have been created.)

The pros and cons: If you're asking yourself, "Who doesn't like cookies?" ask again after a week on this diet. These "treats" come in a variety of flavors, such as chocolate chip and oatmeal raisin, but they basically taste like energy bars. Plus, women who have been living on these cookies haven't necessarily learned how to treat regular food healthfully and may find it hard to trust themselves eating anything once they've slimmed down on this program, says dietitian Susan Bowerman.

The bottom line: It's fine for a few days, but learning how to eat a balanced diet is a smarter approach to losing weight and keeping it off.

The plan: Heidi Klum, Fergie, and many others drink a shot of apple cider vinegar before meals to avoid temptation.

The pros and cons: "This diet rests on the theory that vinegar cuts through fat in your body as it does grease in the kitchen, but that's just an old wives' tale," says Madelyn Fernstrom, director of the University of Pittsburgh Weight Management Center. Still, proponents insist that even just a whiff of the stuff is enough to kill their appetite.

The bottom line: There's no biological reason why vinegar would curb cravings, but it can work in another way. "It becomes a behavioral device—you're reminding yourself that you're trying to lose weight," says Bowerman.

The plan: Celebrities like Keira Knightley and Cameron Diaz have reportedly tried this diet, in which they eat a normal breakfast and dinner, but instead of lunch, they snack all afternoon from a standard-size lunch box filled with 60 percent vegetables, 30 percent protein, and 10 percent fat (such as low-fat dressing, cheese, or peanut butter).

The pros and cons: It's true that you're less likely to feel deprived eating two regular meals and snacking all afternoon. But parceling out your nibbles throughout the day takes discipline—and you're never going to find a jumbo bag of Fritos inside that lunch box.

The bottom line: It's not magic, but it can definitely work—healthy snacking helps boost the metabolism, and a lunch box provides portion control.

The plan: Devotees believe that cooking food destroys its nutritional value, so they eat fruits, vegetables, nuts, and grains that are not heated above 116 degrees (meat and chicken are out).

The pros and cons: It's easy to shed pounds when you're eating lots of unprocessed fruits and vegetables, which are low in saturated fats and calories and high in filling fiber. But let's face it, it's also boring. And unless you're willing to live on salads and smoothies, the diet pretty much requires a personal chef or a raw-food restaurant to make the food more appealing.

The bottom line: It's really hard to stick with this diet—and to do it healthfully. Getting enough protein, calcium, and B-complex vitamins can be a challenge; plus, too much fruit can cause intestinal distress and increase insulin (making the body store calories as fat).